Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 89 near the shore to around 77 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 73 near the shore to around 61 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Sunday: Mostly sunny with isolated showers. Highs around 89 near the shore to around 77 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 86. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 69 to 75. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Sunday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 86. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 76 to 83 in the valleys to around 67 above 4000 feet. East winds up to 15 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then frequent showers after midnight. Lows 61 to 67 in the valleys to around 56 above 4000 feet. East winds up to 20 mph. Chance of rain 80 percent.

Sunday: Mostly cloudy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 76 to 83 in the valleys to around 67 above 4000 feet. East winds up to 15 mph. Chance of rain 80 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 79 to 88. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 74. East winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Partly sunny with scattered showers. Highs 79 to 88. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 87. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 62 to 77. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 87. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Breezy easterly trades will continue today, then briefly ease into the light to moderate range Sunday through Monday as the surface ridge weakens to the north. Showers will primarily favor windward and mauka locations, though a few could reach leeward and interior areas as an upper disturbance drifts southward over the region Sunday. Breezy trades and more stable conditions are expected to return Tuesday, persisting into the latter half of next week.

Discussion

Guidance remains in good agreement, showing breezy easterly trades holding today as the surface ridge stays far north of the state. Satellite imagery shows a decent amount of low cloud coverage over and upstream of the islands (likely due to a weak mid-level trough in the area), which has enhanced windward and mauka shower coverage this morning. Rainfall totals over the past six hours (ending at 2 AM HST) have generally stayed below a tenth of an inch, with the highest accumulations near three-quarters of an inch. Expect this trend to persist through the morning hours today, with mostly light showers passing through.
A slight pattern shift is expected tonight through Monday as upper heights lower in response to a broad, weak upper low drifting southward into the area, while the surface ridge weakens. Lighter trades, combined with a weakened subsidence inversion, could lead to increased windward showers, with some either spilling over into leeward and interior areas or forming over leeward areas due to localized sea breezes in the afternoon. The best chance for thunderstorms will remain north of the state where the better mid-level lapse rates and deeper moisture are expected.
Upper heights will rise Monday night through midweek as the upper low fills and lifts away. This, combined with the surface ridge rebuilding to the north, will support a return to a more stable and breezy trade wind pattern. Although confidence is low this far out, some models suggest an area deeper tropical moisture associated with a disturbance passing far south of the state clipping portions of the area late next week. Expect a wetter trade wind pattern for these areas if this were to materialize.

Aviation

An upper level low is anticipated to move over the state during the weekend time frame. Enhanced SHRA are expected mostly over windward and mauka locations, with limited spillover to leeward areas. MVFR conds can be expected with isolated IFR conds in heavier prolonged SHRA. VFR should generally prevail outside of SHRA activity.
No AIRMETs are in effect. AIRMET Sierra may be needed for mtn obsc for windward locations during the overnight hours through this weekend.

Marine

A high pressure ridge far north of Hawaii will keep fresh to strong easterly trade winds in the forecast today. A cold frontal system passing through the far northern Central Pacific basin will weaken the ridge from Sunday through Monday, briefly easing trade wind speeds into the gentle to moderate range. A Small Craft Advisory (SCA) remains in effect for the windier waters around Maui County and the Big Island. This SCA will likely diminish on Sunday and Monday as the trade winds briefly weaken. Fresh to strong trade winds should return by Tuesday of next week and the trades may approach SCA thresholds for our typical windier waters over the same eastern islands.
Surf along north and west facing shores will trend up beginning next Tuesday in response to a gale racing eastward across the Date Line near the Aleutians this weekend, then into the Gulf of Alaska early next week. Guidance shows this northwest swell peaking locally Tuesday night into Wednesday out of the northwest, then fading Thursday into Friday as it shifts out of a more north-northwest direction.
Surf along south facing shores will remain small through the weekend, with mainly a mix of background long-period southwest and short-period southeast swells moving through. An upward trend is possible Tuesday through midweek due to a slightly larger southwest swell arriving.
Surf along east facing shores will remain small and choppy today, then decrease Sunday into next week as the trades lower locally and upstream across the eastern Pacific.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov